In the production of lift-tab can ends (also known as “easy-open” can ends), the lift-tab is conventionally formed rough-side-up or bottom-side-up. Consequently, it has been necessary to invert the tabs so that they are positioned smooth-side-up, prior to their attachment to can ends. This inversion has generally been accomplished manually, and therefore, it is desirable to provide a method wherein the tab is inverted automatically, thereby saving labor. Alternatively, it is desirable to provide a method of production wherein the lift-tab is formed rough-side-down or top-side-up, thereby eliminating the need for inversion of the lift-tab altogether.
Presses for attaching a lift tab to a can end (known in the industry as “converting” the end to an easy-open can end) are known. Presses of this type are available from the Minister Machine Company of Minister, Ohio. U.S. Pat. No. 4,568,230 shows a layout of a press for processing workpieces into finished can ends with an opening tab attached thereto.
Presses used for the manufacture of easy-open can ends generally comprise a press bed mounted on legs which rest on the floor. Four columns or uprights are mounted on the press bed. The columns or uprights support a crown in which a main drive for the press components is mounted. The columns have slides attached therein for supporting a reciprocating main ram. The main ram carries the upper tooling of the main die set, which cooperates with lower tooling on the bed. The main die set defines a plurality of stations in which the can ends are progressively converted into easy-open can ends. A conveyor carries the can ends into and through the stations of the die set. The tabs are formed by tab tooling, which is supplied with strip stock by a stock feed device. The tab tooling forms a tab and separates it from the strip stock for attachment to a can end.
The tab tooling has conventionally been mounted on the press bed laterally of the conveyor and laterally of the main die. The tab tooling may also be split so that it is arranged laterally on both sides of the main die. A bridge is required to transfer the tab stock strip across the main die set. Such an arrangement is shown in U.S. Pat. No. 4,568,230. The upper tooling is mounted on the main ram of the press.
One of the deficiencies associated with this arrangement of the tooling is that it is difficult to access the tooling for maintenance. Access to the can end tooling is difficult due to the presence of the tab tooling on one side of the main die and the tab tooling and tab stock feed device on the other side of the main die. The lateral placement of the tab tooling also increases the depth of the press from front to back. This requires a larger bed which increases the weight of the press and reduces its speed.